Hey guys, I barely post on here, but I need some guidance and possibly a solution. I have a 98 Gs400.
So the story/: It all started the day before Thanksgiving. I was driving up a busy hill, and all of the sudden, my battery light turns on and my car suddenly loses power. My car sputters and luckily I get to a safe spot. I try starting it up but there is barely any power to it. So crap, I was like what the hell! My first thing was maybe it's my alternator?
So I get it towed to my house, and my dad (who is sort of a handy man, but self anointed mechanic) jump starts it and it starts up. So possibly my battery? But i just replaced my battery on January 2011. I take the battery to an automotive store and they tested it and it is completely drained. So they replaced it free of charge. I put the battery in and it works fine, but my battery light is still on . I still suspect it being the alternator. They ran some tests on the alternator and they said everything seemed fine with it but...it registered that there was a low charge.

So that is my dilemma and hopefully i can get some of your input and possible solution, and maybe a next step. (sorry for the long post)

 

if the battery was completely drained. the car was most likely running on just the battery with little to no help from the alternator. Check the connection at the alternator terminal and make sure its tight and check if there is any corrosion. Could be a bad connection or the alternator needs to be replaced.

whats the voltage at the battery when the car is running?

whats the voltage at the alternator when the car is running?

 

a bad connection is very rare. it is definitely the alternator. for an alternator to run properly it needs to put out between 13.5 to 15 volts with no loads. when the stereo or lights are turned on it may dip a little but should not go below the 13.5 volts. so if your alternator has low output then replace the alternator. the light on the dash will turn off and you will no longer be killing batteries

 

Sounds IDENTICAL to my situation back in April. The alternator was toast. It's not a bad idea to check on the power steering system, as it leaks above the alternator and eventually kills it.

 

check for leaks above the alternator like thomas said, mine was leaking from the valve cover and ruined two alternators before i fixed the problem

 

Is there a way to test the alternator. I took my car to get my alternator tested, and it was was registering about 15 I believe. He said it was fine, but that's with just "the test."

 

I had AAA come to my house, the guy tested my alternator and said all was well and that the car just needed to be driven around. I took the guy's advice and ended up stranded.

 

Replace the alternator.
Not very hard, there's a DIY thread for it.
Fix PS leak if there's any and you'll have peace of mind.